Throughout spermatogenesis, developing germ cells at different stages of their development must attach to the seminiferous epithelium via specialized cell junctions at the Sertoli-germ cell interface. As such, disruption of germ cell adhesion, even transiently, can lead to germ cell loss from the epithelium, resulting in infertility. Studies completed during the past grant period have shown that Adjudin[unreadable] [formerly called AF- 2364, 1-(2,4-dichlorobenzyl)-7H-indazole-3-carbohydrazide] is a promising candidate for male contraception since it effectively depletes germ cells, particularly elongating/elongate spermatids, round spermatids, and spermatocytes, but not spermatogonia, from the epithelium in adult rats. More important, studies performed by licensed toxicologists according to FDA guidelines to assess the acute toxicity, mutagenicity, and genotoxicity of Adjudin have shown that it is safe for its further development. In a subsequent subchronic toxicity study, however, it was shown that Adjudin has a narrow margin between its safety and efficacy. To circumvent this issue, Adjudin was conjugated to an FSH mutant in which the intrinsic hormonal activity of the mutant was stripped without compromising its FSH receptor binding activity. Most importantly, its efficacy was significantly improved. The P.I. has now proposed studies to develop techniques for GMP production of this Adjudin-FSH mutant conjugate in collaboration with an industrial partner, and to develop alternative administrative routes, such as a gel patch or nasal spray for its absorption instead of parental administration, using technologies established in the field and at the Population Council. Once the efficacy and bioavailability of the conjugate are established, its safety issue will be carefully evaluated by subchronic toxicity studies in rats and dogs to assess the margin between its safety and efficacy. Furthermore, contemporary techniques of biochemistry, molecular biology and cell biology will be used to continue the ongoing research in this laboratory to probe the molecular mechanism(s) of action of Adjudin including its cellular effects on Sertoli and germ cells in the seminiferous epithelium. We will also identify the cellular target(s) of Adjudin in the testis, including mapping the phosphorylation site(s) in integrin, since its activation likely triggers the Adjudin-induced germ cell loss from the testis. In short, this proposal will continue the productive research in the P.l.'s laboratory, which will lead to a Phase 1 clinical study of Adjudin.